This proposal is designed to study both prospectively and retrospectively a group of juvenile diabetic patients in an attempt to determine from a clinical, pathological, and metabolic approach the importance and extent of cardiovascular disease. The patient population will include approximately 200 living juvenile diabetics who have been personally followed by one of the co-investigators (HCK) for periods up to 25 years. The median age at diagnosis of diabetes is 9 years (0-16), and the median years of duration of disease is 18 (10-43). This group of long-term juvenile diabetics which has been exceptionally closely followed has already been the subject of several reports. The objective of this proposal is to study in depth the various manifestations of cardiac disease in the juvenile diabetic population. It is proposed to develop clinical, pathological and metabolic approaches to this problem in order to gain a better understanding of the type of coronary (and possibly myocardial) disease that occurs in the juvenile diabetic. It is also proposed to determine the value of certain laboratory techniques in an effort to recognize at an earlier time the occurrence of subclinical coronary artery disease in the juvenile diabetic.